One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
FIGS. 1-3 illustrate a conventional disk drive unit 100. As illustrated, the disk drive unit 100 comprises a base plate 20, a set of components (will be described hereinafter) received in the base plate 20 and a top cover 10 mounted on the base plate 20 by a plurality of screws 30. The set of components are enclosed in a space defined by the base plate 20 and the top cover 10.
As best shown in FIG. 2, the base plate 20 comprises an oblong bottom portion 225 and a sidewall 26 extending perpendicularly from a perimeter of the bottom portion 225. Four posts 24, each of which has a screw hole 21 defined therein, are formed at four corners of the base plate 20 respectively for mounting the top cover 10 on the base plate 20.
Now describe the components received in the base plate 20. Referring to FIG. 2, a disk 27 having a plurality of concentric tracks is disposed in the base plate 20 for recording digital information. The disk 27 is mounted to a spindle motor 22 and can be rotated by the spindle motor 22. Also disposed in the base plate 20 is a head stack assembly (HSA) 23 which can rotate around a bearing assembly 233. A slider 234 with a reading/writing transducer is mounted at a distal end of the HSA 23 and located above a surface of the disk 27. In addition, a flexible printed circuit (FPC) 25 is contained in the base plate 20. One end of the FPC 25 is electrically connected with the HSA 23, while the other end is electrically connected to an external control system such as a printed circuit board assembly (PCBA, not shown). In operation, the disk 27 rotates at a high speed such that an aerodynamic interaction is generated between the surface of the disk 27 and the slider 234, thus making the slider 234 flying above the disk 27 at a predefined flying height. Moreover, driven by the external control system through the FPC 25, the slider 234 can move from track to track across the surface of the disk 27 and achieve data reading/writing operation.
The top cover 10 is used to cover the components mounted in the base plate 20 and protect them from being damaged by external forces. The top cover 10 has a shape corresponding to the base plate 20, namely, an oblong shape. The top cover 10 comprises a top portion 15 and a sidewall 16 extending perpendicularly from the perimeter of the top portion 15. Several radial extrusions 12 are stampingly formed on the top portion 15 for enhancing structure rigidity. In addition, corresponding to the four posts 24 of the base plate 20, four through holes 14 are defined at four corners of the top cover 10 respectively, through which a plurality of screws 30 (see FIG. 1) can pass and be screwed to respective screw holes 21 of the posts 24, thereby securing the top cover 10 to the base plate 20. Moreover, a securing hole 18 is defined in the top portion 15 to secure the bear assembly 233 of the HSA 23 between the top cover 10 and the base plate 20.
With the development of the technology, disk drive units become smaller and smaller in size such that they can be assembled into computers of small form factor for example laptop computers, thus making computers have a smaller volume and become more convenient and portable for users. However, the conventional disk drive unit described above fails to satisfy this requirement for reduction in volume.
Commonly, for a typical disk drive unit, an airflow channel of suitable width must be formed between an inner sidewall of the disk drive unit and periphery of a disk disposed in the disk drive unit, so that when the disk rotates, sufficient airflow can be generated along surface of the disk, hence enabling a slider to be floated above the disk surface. In addition, for a typical disk drive unit, the top cover is normally thinner than the base plate for reducing whole weight of the disk drive unit. However, in a conventional disk drive unit as that shown in FIG. 3, since the sidewall 26 of the base plate 20 is designed to be higher than the disk 27 with respect to the bottom portion 225 (and in the figure, the height difference is h1), the airflow channel 235 having a width of d1 is defined between the inner side surface of the sidewall 26 and periphery of the disk 27. This width d1 is the minimum width for the airflow channel 235 and cannot be reduced any more; otherwise the airflow generated along the surface of the disk 27 will be insufficient for floating the slider above the disk surface. As a result, size of the base plate 20 cannot be reduced any more. Correspondingly, the top cover 10 mounted to the base plate 20 is also difficult to be reduced in size, and since the top cover 10 is thinner than the base plate 20, a distance d2 larger than d1 is defined between an inner side surface of the top cover 10 and the periphery of the disk 27. This distance d2 makes the top cover 10 occupy a huge space, thus causing waste in space. Resultantly, the conventional disk drive unit suffers from a big profile.
Thus, there is a need to provide an improved disk drive unit that does not suffer from the above-mentioned drawbacks.